Electromagneti pumps for liquid metals

ABSTRACT

A gapless and an air-gap magnetic circuit are separated by a clearance which accommodates a straight conduit conveying a liquid metal. The air-gap magnetic circuit is the multipole core of an A.C. electromagnet and serves to establish a magnetic field in the liquid metal. The gapless magnetic circuit is a polyphase transformer with single-turn secondary windings formed by the liquid metal and a conductor enveloping the transformer core. The gapless magnetic circuit induces an electric current in the liquid metal. The magnetic field and the electric current interact to produce an electromagnetic head.

FIP85132 KR United States Patent [191 Radchenko et al.

[ 1 3,708,246 51 Jan.2, 1973 [73] Assignee: Otdel [54]ELECTROMAGNETILPUMPS FOR LIQUID METALS [75] Inventors: RuslanVasilievich Radchenko; Stanislav Alexandrovich Mokrushin, both ofSverdlovsk, U.S.S.R.

Fiziko-Tekhnicheskilch Problem Energetiki Uralskogo Filiala An SSRFiliala Am SSSR, Sverdlovsk, U.S.S.R.

'22 Filed: July 12, 1971 21 Appl. No.: 161,487

521 U.S.Cl. ..;.417/s0,310/11,417/49 51 lnt.Cl. ..H02k45/00 [58]Fieldofsearch ..310/11;417/49,50

[56] References Cited UNITED STATES PATENTS 2,397,785 4/1945Friedlander........... ..417/50 2,686,474 8/1954 Pulley ..4-17/50FOREIGN PATENTS OR APPLICATIONS 847,492 10/1956 GreatBritaim......417/50 745,807 10/1954 Sweden ..4l7/50 Primary Examiner-William L.Freeh Assistant Examiner-.Iohn T. Winburn Attorney-Eric H. Waters et al.

[ 5 7] ABSTRACT A gapless and an air-gap magnetic circuit are separatedby a clearance which accommodates a straight conduit conveying a liquidmetal. The air-gap magnetic circuit is the multipole core of an AC.electromagnet and serves to establish a magnetic field in the liquidmetal. The gapless magnetic circuit is a polyphase transformer withsingle-turn secondary windings formed by the liquid metal and aconductor enveloping the transformer core. The gapless magnetic circuitinduces an electric current in the liquid metal. The magnetic field andthe electric'current interact to produce an electromagnetic head.

2 Claims, 3 Drawing Figures ELECTROMAGNETI PUMPS FOR LIQUII) METALS Thepresent invention relates to an improvement in means for the handling ofliquids, and more specifically to electromagnetic pumps for liquidmetals, and may be utilized in, say, nuclear-power engineering to pump aliquid-metal heat-carrying agent in nuclear reactors or to convey moltenmetals in metallurgy.

In the prior art, there is an electromagnetic pump which has twoconduits with thin electrically conducting walls. These conduits arepart of asingle secondary turn of a transformer with a gapless magneticcircuit. The primary (power winding of this transformer is energizedfrom one phase of a polyphase source and induces current in thesecondary turn. In the conduits, a magnetic field is established by afield circuit connected to another phase of the same source in such amanner that the current and the field are in phase. The in-phase currentand field interact to produce a head. The magnetic flux consecutivelylinks the two conduits, while the current in the conduits flows inopposite directions. Therefore, in order to produce a total head, theconduits are interconnected by an U-shaped hose.

A disadvantage of this prior-art arrangement consists in that theU-shaped hose interconnecting the conduits inevitably entailsconsiderable hydraulic losses and markedly handicaps the construction ofelectromagnetic pumps of higher capacity. As a rule, the conduits in apump are arranged one above the other, which increases the overallmagnetic gap and impairs tI-Ie power factor of the entire system.

Another disadvantage of the pump is that there is an unbalanced load onthe phases of the supply source.

It is an object of the present invention to provide an electromagneticpump which materially reduces hydraulic losses and places a balancedload on the phases of the supply source.

With this and other objects in view, the present invention resides inthat in an electromagnetic pump having a conduit placed between agapless and an air-gap magnetic circuit producing an electric currentand a magnetic field at right angles to each other, according to theinvention the air-gap magnetic circuit is a multipole core of an A.C.electromagnet, carrying field windings, and the gapless magnetic circuitis a polyphase transformer with its single-tum secondaries formed by theliquid metal in the portions of the conduit where the current andmagnetic field interact and by a conductor which is in contact withthemetal and envelopes both the liquid metal and the transformer core,such that the number of poles and secondary turns is a multiple of thenumber of phases in the source energizing the magnetic circuits and theconduit between the magnetic circuits is made straight.

Owing to a straight conduit, the hydraulic losses in the pump arematerially reduced, while its magnetic circuits impose a balanced loadon the supply source.

It is preferable to offset the turns in the outer openings of thepolyphase transformer from center towards tHe outer walls.

The invention will be more fully understood from the followingdescription of a preferred embodiment when read in connection with theaccompanying drawings wherein:

FIG. 1 is a circuit schematic diagram of a pump according to theinvention, operating on a three-phase pp y FIG. 2 is section 11- of FIG.1;

FIG. 3 shows the same as FIG. 1, except that the turns in the outeropenings of the transformer core are offset.

Referring to FIG. 1, there is a pump comprising a gapless magneticcircuit 1 which is a three-phase transformer with primary windings 2.The electric power to be converted into a useful head in a conduit, aswill be shown shortly, is applied to the transformer, and so for brevitythe circuit containing this transformer or the transformer proper willbe referred to as the power circuit and the power transformer.

The air-gap magnetic circuit 3 is the air-gap threepole core of an A.C.electromagnet, with windings 4, which serves to set up a magnetic fieldin a conduit 5. The electric power applied to this circuit goes tosustain the losses involved in establishing the magnetic field, and sofor brevity it will be called the field circuit.

The portions 6 of the conduit where the electric current and themagnetic field interact are located opposite the poles of the air-gapmagnetic circuit. The number of poles 7 is a multiple of the number ofphases in the supply source. The conductors 9 (FIG. 2) enveloping thecore 8 of the power transformer are in electric contact with the liquidmetal, so that both the conductors 9 and the liquid metal within theportions 6 of the conduit 5 make up loops which are the secondaries ofthe power transformer.

The number of secondary turns thus formed should be a multiple of thenumber of phases in the supply source.

At the inlet to and the outlet from each portion 6 of the conduit 5,there are longitudinal partitions 10 which prevent the current fromspreading into other portions of the conduit, where the current andfield do not interact.

In the outer openings 11 of the transformer core the conductors 9 areoffset from the middle of the openings towards the outer walls as shownin FIG. 3 in order to minimize eddy-current losses. With thisarrangement of the conductors, eddy-current losses are practicallynon-existent.

The gapless and air-gap magnetic circuits 1 and 3 are arranged so as toform a clearance for the straight conduit 5.

The magnetic fluxes due to the field windings 4 have their path in thegap between the poles 7 of the field circuit and the core 8 of the powercircuit. In the core 8, these fluxes are added together according to thephase shift between them. The fluxes due to the field circuit do notextend into other parts of the power transformer, because theirreluctance is high in com-' parison with that of the core 8. The totalmagnetuc flux in the core 8 is the sum of the magnetic fluxes due toeach pair of transformer primary and secondary windings operating on thesame phase. Therefore, the dimensions of the core 8 will be decided bythe crosssectional area required to accommodate the aggregate magneticflux of the power and field circuits.

Within the portions 6, the magnetic field acts across the conduit 5,while the current in the secondary windings within the same portions isat right angles to the field. The useful head is produced as an outcomeof interaction between the mutually perpendicular current and field andis directed along the conduit 5. The head is a maximum when the currentand field within each of the portions 6 are in phase. This phaserelationship can be obtained by suitably connecting the windings to thephases of the supply source. Since in the airgap magnetic circuit thenumber of poles is a multiple of the number of phases in the supplysource, the load willalways be balanced, as long as there are at leasttwo phases in the source.

What is claimed is:

1. An electromagnetic pump for liquid metals, comprising: a practicallystraight conduit for the liquid metal to be handled; a gapless and anair-gap magnetic circuit separated by a clearance accommodating saidconduit; said gapless and air-gap circuits respectively induce in themetal an electric current and a magnetic field which are at right anglesto each other and interact to produce an electromagnetic head movingsaid metal in said conduit; said air-gap magnetic circuit being amulti-pole a.c. electromagnet and said gapless magnetic circuit being apolyphase transformer with as many pairs of primary and secondarywindings as there are poles in the multipole electromagnet; saidsecondary windings being formed by said liquid metal in portions of saidconduit where the current and field interact and by a conductor whichtogether with the liquid metal envelopes a core of said transformer; andthe number of said poles in the air-gap magnetic circuit and ofsecondary windings is a multiple of the number of phases in said powersource.

2. An electromagnetic pump, as in claim 1, in which the secondaryconductors in the outer openings of the transformer core are offset fromcenter towards the outer walls.

1. An electromagnetic pump for liquid metals, comprising: a practicallystraight conduit for the liquid metal to be handled; a gapless and anair-gap magnetic circuit separated by a clearance accommodating saidconduit; said gapless and air-gap circuits respectively induce in themetal an electric current and a magnetic field which are at right anglesto each other and interact to produce an electromagnetic head movingsaid metal in said conduit; said air-gap magnetic circuit being amulti-pole a.c. electromagnet and said gapless magnetic circuit being apolyphase transformer with as many pairs of primary and secondarywindings as there are poles in the multipole electromagnet; saidsecondary windings being formed by said liquid metal in portions of saidconduit where the current and field interact and by a conductor whichtogether with the liquid metal envelopes a core of said transformer; andthe number of said poles in the air-gap magnetic circuit and ofsecondary windings is a multiple of the number of phases in said powersource.
 2. An electromagnetic pump, as in claim 1, in which thesecondary conductors in the outer openings of the transformer core areoffset from center towards the outer walls.